1. Field of the Invention
The present invention relates to a method of manufacturing a substrate, a method of manufacturing a liquid ejection head, a liquid ejection head and an image forming apparatus, and more particularly, to a method of manufacturing a substrate, a method of manufacturing a liquid ejection head, a liquid ejection head and an image forming apparatus, in which three-dimensional wiring is formed.
2. Description of the Related Art
An image forming apparatus has an ink ejection head having an arrangement of a plurality of nozzles (ejection ports) for ejecting ink, and forms images on a recording medium, such as paper, by ejecting ink from the nozzles toward the recording medium, while moving the ink ejection head and the recording medium relatively to each other.
In the ink ejection head in the image forming apparatus, for example, piezoelectric bodies are used as pressure generating devices for ejecting ink, and a diaphragm which forms one wall of the pressure chambers is deformed by the deformation of the piezoelectric bodies, thereby changing the volume of the pressure chambers, and causing ink inside the pressure chambers to be ejected from the nozzles in the form of droplets.
In recent years, there have been demands for improved image quality and higher recording speeds in image forming apparatuses having ink ejection heads, and in order to achieve this, it is essential to increase the number of nozzles and to arrange these nozzles at higher density.
In order to achieve an increased number of nozzles and higher nozzle density, it is necessary to arrange the pressure chambers connected to the nozzles at high density, as well as laying out the electrical wires (drive wires) which supply drive signals to the piezoelectric bodies disposed corresponding to the respective pressure chambers, at high density also.
Furthermore, in general, a mode is known in which piezoelectric bodies are driven in a so-called “bending distortion mode”, and in this mode, it is necessary to ensure sufficient spaces to prevent obstruction of the movement of the piezoelectric bodies, on the side of the piezoelectric bodies reverse to the side where they are fixed to the diaphragm. Therefore, in general, the connection between the upper electrode of the piezoelectric body and the external wire must pass through the space.
With the object of simplifying the structure of an inkjet head and reducing the size of the inkjet head, Japanese Patent Application Publication No. 2003-136721 (and in particular, FIGS. 7 to 9) discloses a head having a bonding member connected to the piezoelectric body side of a flow channel forming substrate having pressure chambers, a diaphragm and piezoelectric bodies, in which installation sections for connecting external wires are provided on the bonding member in regions corresponding to the piezoelectric bodies, and drive wires (connection wires) are installed, one end of each wire being connected to the installation section on the bonding member, and the other end thereof being connected to the piezoelectric body. For these drive wires, more specifically, it is disclosed to form drive wires by wire bonding so as to pass along through holes (through grooves) which pass through the bonding member. Furthermore, a thin film (wiring film) is formed by sputtering on the internal face (oblique surface) of the through holes (through grooves) which have an oblique surface, as well as passing through the bonding member in the thickness direction.
If it is sought to install wires at high density in a case where through holes are formed in the thickness direction of a bonding member and drive wires are formed by wire bonding so as to pass through these through holes, as disclosed in Japanese Patent Application Publication No. 2003-136721, then there may be a problem that the wires contact with each other, and moreover, the through holes must be formed to have a diameter allowing a wire bonding probe to be inserted. Furthermore, the cross-sectional surface area of the drive wires must be made smaller than the surface area of the opening of the through holes. Therefore, in practice, it is not possible to install the wiring to a high density.
Moreover, if through holes are opened in the thickness direction of the bonding member and a thin film is formed by sputtering on the internal surface of the through holes, then after forming the thin film by sputtering, a patterning step is required in order to achieve independent drive wires for each piezoelectric body.